Method of cutting a sheet and reducing the remnant material

ABSTRACT

The invention relates to a method of cutting a sheet-like piece into one or several smaller pieces by using camera means and a controllable cutting apparatus, the directions and values of the coordinate systems of which are calibrated to correspond to each other. In the method the following measures are taken: the piece to be cut is placed on a cutting surface located within the recording area of the camera means, the piece is photographed by the camera means and on the basis thereof the outlines of the piece are determined and the information on the outlines of the piece is input into the positioning system, where the cutting paths are established and input into the control system of the cutting device, which determines necessary parameters for the cutting and on the basis of these, controls the cutting of the piece into parts according to given instructions.

The invention relates to a method of cutting a sheet-like piece byutilizing camera means and a controllable cutting apparatus inaccordance with the preamble of claim 1.

A lot of so-called remnant sheet is produced by the shipbuilding work,when larger sheet objects are manufactured by thermal cutting. On theother hand a ship comprises a great number of small standard components,the annual need of which is several thousands of pieces, and the aim isto use remnant sheet as a material for these components, where possible.While manufacturing standard components, the machine operator has to useexcessively much time for utilizing the remnant pieces. Today, theutilization of remnant sheet is not cost-effective from the technicaland economical point of view and the problem when using remnant materialhas been the difficulty in positioning standard components on a remnantsheet having an irregular shape, and thus the scrub percentage has beenfairly high. Conventionally, the utilization of remnant material hasstayed on a level, where the machine operator measures by hand arectangular area on the remnant sheets, inputs the data into the machinecontrol and starts positioning components on the defined area. Being atask of the machine operator the positioning is in its present form fartoo time-consuming, and the outcome is not economical in terms ofworking hours and consumption of material. In practice, the machineoperator has to make also a physical effort when taking the cuttingmachine to the starting point of the cutting program.

An aim of the present invention is to overcome the disadvantages relatedto prior art and provide a novel solution, where said disadvantages canbe eliminated as efficiently as possible.

The aim of the invention can be achieved as is described in claim 1 andin the other claims.

According to the invention following measures are taken: the piece to becut is placed on a cutting surface located within the recording area ofcamera means, the piece is photographed by the camera means and on thebasis thereof the outlines of the piece are determined and theinformation on the outlines of the piece is input into the positioningsystem, where the cutting paths are established and input into thecontrol system of the cutting machine, which determines necessaryparameters for the cutting and on the basis of these, controls thecutting of the piece into parts according to given instructions. Thus,the invention enables the use of machine vision for defining the sheetblank so as to provide and implement a cutting program. Preferably, alsoautomation may be applied to the positioning of the pieces to be cut onthe remnant sheet. Thus the invention enables an economical utilizationof remnant sheet material in the positioning the pieces to be cut, andminimises manual work and the scrub percentage of the remnant sheetmaterial. Here, the outlines of the piece also refer to the shape ofsuch parts of the pieces, e.g. openings, which remain inside the piece.Also, the invention is preferably applicable to the utilization ofremnant sheet objects, which are irregular in shape, in a most optimalway.

Once the outlines and dimensions of the piece have been determined,positioning data is created by selecting at least one type of a smallpart and adding a desired number of said at least one type of smallparts to the outline image inside the outlines. For the positioning asuitable program may be used for instance by selecting a certain type ofa small part from the macro-library, whereby the program fills thesheet-like piece with said parts. The positioning may also be based onselecting several different kinds of small parts. Alternatively, alsothe operator himself may draw by the program a desired kind of a smallpart and place a certain number of these on the sheet-like piece.

In the automatic positioning on a remnant sheet the cutting paths,starting points and volumes as well as the use of material areoptimised. Also the starting point of the cutting and the cutting pathmay be determined either by the operator or automatically. After thedetermination, the positioning data is input into the control system ofthe cutting apparatus, whereby the operation of the cutting machinechanges from an incremental, i.e. from a sheet blank specific,coordinate system proportioned to the zero point over to an absolutecoordinate system, i.e. to a coordinate system covering the whole workstation. A numerically controlled flame cutting machine, a manipulatoror a robot is preferably used as a cutting apparatus.

As ancillary equipment while photographing the object, a light source tobe reflected, most preferably a laser bar, may be used to facilitate thedetectability and/or to provide additional information. In the methodaccording to the invention the working area is illuminated forphotographing to such an extent that the illumination conditions are asconstant as possible so as to make the outlines and position of thepiece visible with sufficient accuracy. The illumination and the bars ormatrices to be reflected facilitating the detectability arecomplementary to each other. The photographing according to the methodmay be performed by one or several cameras, preferably CCD-cameras,which may be located in the cutting apparatus, in a separate portalmoving on the same guide rails as the cutting apparatus or in externalstructures, e.g. at the ceiling of the working area, or by means of aseparate guide rail in outside structures.

The pieces to be cut compose parts of a metal structure, which mostpreferably may be intended for a watercraft, ship or another marineequipment, but the invention may as well be applied to other kinds ofobjects, where sheet metal pieces are utilized.

In the following the invention is described by way of example withreference to the attached drawings, in which

FIG. 1 shows a functional diagram for utilizing remnant material in themanufacture of sheet objects; and

FIG. 2 shows a positioning layout.

In a machining arrangement 1 according to FIG. 1, i.e. in this casethermal cutting, an image of the cutting area 3 of a cutting apparatusis provided by camera means 2 to be attached to a cutting machine, to aseparate guide rail or to structures surrounding the machine. The shapeand dimensions of the outlines of a sheet blank 4 comprising a remnantsheet and located within the cutting area 3 are determined by means ofthe image provided by the camera. The sheet blank 4 is placed on acutting surface 5, which may comprise for instance a floor or amachining table. The determination of the dimensions may be performed bysoftware according to software algorithms or manually by the operator bypointing at the display. As ancillary equipment for the determination anillumination and a light source to be reflected, preferably ahelium-neon laser bar, may be used for facilitating the detectability.The result of the determination is data, i.e. so-called image data 6,including the dimensions of the outlines of the sheet blank 4 and itslocation in the working area 3, which data is transferred over to apositioning system 7, where a desired number of certain type of smallparts is placed on the area. For instance a certain type of a small partmay be selected from the macro-library and the positioning program maybe arranged so as to fill the sheet blank with said parts.Alternatively, also the operator himself may draw by the program a smallpart having a desired shape and place a certain number of these parts onthe sheet blank, and if desired, a certain number of some other kinds ofsmall parts, if there is still open space on the sheet blank. Thepositioning data is then input into the control system of the cuttingapparatus, which actuates a cutting program 8.

The positioning system 7 may be located either on a separate computer 7or in conjunction with a machine control 9. Information on a sheet blank4 having any kind of a shape is received easily and fast with theassistance of the system and it is possible to optimise the use of theblank and minimize the scrub percentage by means of computer-basedautomatic positioning. In addition to the dimensions of the sheet blank4, the machine vision system is capable of indicating also the positionof a reference angle or starting angle in the working area 3 of thecutting apparatus (not shown in detail), whereby a separate relocationof the cutting apparatus, which used to be carried out manually, isunnecessary, and the cutting 10 of the sheet blank 4 may be started.Thus both time and material can be saved by the invention, meanwhile theoperation efficiency improves and the costs decrease.

The cutting may be performed by methods known per se, e.g. by gascutting or plasma cutting. One advantageous method is numericallycontrolled thermal cutting, where the parameters for cutting, e.g. thecutting speed, the size of the cutting grooves etc., may be determinedby numerical control. The cutting apparatus may run itself to thestarting point and start the cutting.

FIG. 2 shows an example of a positioning and cutting layout, which maybe realized by inputting the layout into a numerically controlledcutting machine. Here, a number of sheet-like small parts 4 a, which areall alike, are placed on a sheet blank 4. Some of these could, ofcourse, be replaced by other kinds of parts. The cutting directions areindicated by arrows.

It is evident for a person skilled in the art that the invention is notlimited to the above-described application, but various modifications ofthe invention are conceivable in the scope of the inventive conceptiondefined by the appended claims.

1-7. (canceled)
 8. A method of cutting a sheet-like piece of metal intoone or several smaller pieces by using camera means and a controllablecutting apparatus, the directions and values of the coordinate systemsof which are calibrated to correspond to each other, characterized inthat following measures are taken: the piece to be cut is placed on acutting surface located within the recording area of the camera means,the piece is photographed by the camera means and on the basis thereofthe outlines of the piece are determined, the information on theoutlines of the piece is input into the positioning system, wherepositioning data is created by selecting at least one type of a smallpart and, when applicable, adding a desired number of said at least onetype of small parts into the outline image inside the outlines and thecutting paths are established and input into the control system of thecutting machine which determines necessary parameters for the cuttingand on the basis of these the cutting of the piece into parts is carriedout on said cutting surface under the control of the said control systemaccording to given instructions.
 9. A method according to claim 8,characterized in that also the starting point of the cutting and thecutting path are determined automatically or by operator-aided means,and the positioning data is input into the control system of the cuttingapparatus.
 10. A method according to claim 8, characterized in that inthe automatic positioning on the sheet the cutting paths, startingpoints and volumes as well as the use of material are optimized.
 11. Amethod according to claim 8, characterized in that the operation of thecutting apparatus changes from an incremental, i.e. a sheet blankspecific, coordinate system proportioned to the zero point over to anabsolute coordinate system, i.e. to a coordinate system covering thewhole work station.
 12. A method according to claim 8, characterized inthat a numerically controlled thermal cutting machine, a manipulator ora robot is used as a cutting apparatus.
 13. A method according to claim8, characterized in that as ancillary equipment while photographing theobject, a light source to be reflected, most preferably a laser bar, maybe used to facilitate the detectability and/or to provide additionalinformation.
 14. A method according to claim 8, characterized in thatthe pieces to be cut compose parts of a metal structure, for instance awatercraft, ship or another marine equipment, a bridge, paper machine,building, vehicle such as a train, lorry, mining vehicle or a tank or aplatform structure.